Add a warning when trying to create a double redirect

Shows a warning when trying to create a redirect that points to another
redirect.

Bug: T326056
Change-Id: Ieb51dde88ce6c23753f74191a85cd40f0bfbd864

3 files changed, 151 insertions, 0 deletions

diff --git a/includes/editpage/Constraint/DoubleRedirectConstraint.php b/includes/editpage/Constraint/DoubleRedirectConstraint.php
new file mode 100644
index 000000000000..fd5ee1ab04cc
--- /dev/null
+++ b/includes/editpage/Constraint/DoubleRedirectConstraint.php
@@ -0,0 +1,104 @@
+<?php
+/**
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ */
+
+namespace MediaWiki\EditPage\Constraint;
+
+use MediaWiki\Content\Content;
+use MediaWiki\Linker\LinkTarget;
+use MediaWiki\Page\RedirectLookup;
+use MediaWiki\Title\Title;
+use StatusValue;
+
+/**
+ * Verify the page does not redirect to another redirect unless
+ *  - the user is okay with a double redirect, or
+ *  - the page already redirected to another redirect before the edit
+ *
+ * @since 1.44
+ * @internal
+ */
+class DoubleRedirectConstraint implements IEditConstraint {
+
+	private bool $allowDoubleRedirects;
+	private Content $newContent;
+	private Content $originalContent;
+	private LinkTarget $title;
+	private string $result;
+	private RedirectLookup $redirectLookup;
+
+	/**
+	 * @param bool $allowDoubleRedirects
+	 * @param Content $newContent
+	 * @param Content $originalContent
+	 * @param LinkTarget $title
+	 */
+	public function __construct(
+		bool $allowDoubleRedirects,
+		Content $newContent,
+		Content $originalContent,
+		LinkTarget $title,
+		RedirectLookup $redirectLookup
+	) {
+		$this->allowDoubleRedirects = $allowDoubleRedirects;
+		$this->newContent = $newContent;
+		$this->originalContent = $originalContent;
+		$this->title = $title;
+		$this->redirectLookup = $redirectLookup;
+	}
+
+	public function checkConstraint(): string {
+		if ( !$this->allowDoubleRedirects ) {
+			$newRedirectTarget = $this->newContent->getRedirectTarget();
+
+			if ( $newRedirectTarget !== null && $newRedirectTarget->isRedirect() &&
+				!$newRedirectTarget->equals( $this->title ) ) {
+
+				$currentTarget = $this->originalContent->getRedirectTarget();
+
+				// fail if there was no previous content or the previous content already contained a double redirect
+				if ( !$currentTarget || !$currentTarget->isRedirect() ) {
+					$this->result = self::CONSTRAINT_FAILED;
+
+					return self::CONSTRAINT_FAILED;
+				}
+			}
+		}
+		$this->result = self::CONSTRAINT_PASSED;
+
+		return self::CONSTRAINT_PASSED;
+	}
+
+	public function getLegacyStatus(): StatusValue {
+		$statusValue = StatusValue::newGood();
+		if ( $this->result === self::CONSTRAINT_FAILED ) {
+			$realRedirectTarget = $this->redirectLookup->getRedirectTarget( $this->newContent->getRedirectTarget() );
+			$realTargetTitle = Title::castFromLinkTarget( $realRedirectTarget );
+
+			$statusValue->fatal(
+				'edit-constraint-doubleredirect',
+				wfEscapeWikiText( $realTargetTitle->getPrefixedText() )
+			);
+			$statusValue->value = self::AS_DOUBLE_REDIRECT;
+		}
+
+		return $statusValue;
+	}
+
+}
diff --git a/includes/editpage/EditPage.php b/includes/editpage/EditPage.php
index d492ce5a0b3c..b853e5d18067 100644
--- a/includes/editpage/EditPage.php
+++ b/includes/editpage/EditPage.php
@@ -45,6 +45,7 @@ use MediaWiki\EditPage\Constraint\BrokenRedirectConstraint;
 use MediaWiki\EditPage\Constraint\ChangeTagsConstraint;
 use MediaWiki\EditPage\Constraint\ContentModelChangeConstraint;
 use MediaWiki\EditPage\Constraint\DefaultTextConstraint;
+use MediaWiki\EditPage\Constraint\DoubleRedirectConstraint;
 use MediaWiki\EditPage\Constraint\EditConstraintFactory;
 use MediaWiki\EditPage\Constraint\EditConstraintRunner;
 use MediaWiki\EditPage\Constraint\EditFilterMergedContentHookConstraint;
@@ -269,6 +270,12 @@ class EditPage implements IEditObject {
 	/** @var bool */
 	private $allowBrokenRedirects = false;
 
+	/** @var bool */
+	private $doubleRedirect = false;
+
+	/** @var bool */
+	private $allowDoubleRedirects = false;
+
 	/** @var string */
 	private $autoSumm = '';
 
@@ -1327,6 +1334,7 @@ class EditPage implements IEditObject {
 		$this->allowBlankArticle = $request->getBool( 'wpIgnoreBlankArticle' );
 		$this->allowSelfRedirect = $request->getBool( 'wpIgnoreSelfRedirect' );
 		$this->allowBrokenRedirects = $request->getBool( 'wpIgnoreBrokenRedirects' );
+		$this->allowDoubleRedirects = $request->getBool( 'wpIgnoreDoubleRedirects' );
 
 		$changeTags = $request->getVal( 'wpChangeTags' );
 		if ( $changeTags === null || $changeTags === '' ) {
@@ -1860,6 +1868,7 @@ class EditPage implements IEditObject {
 			case self::AS_BLANK_ARTICLE:
 			case self::AS_SELF_REDIRECT:
 			case self::AS_BROKEN_REDIRECT:
+			case self::AS_DOUBLE_REDIRECT:
 			case self::AS_REVISION_WAS_DELETED:
 				return true;
 
@@ -2498,6 +2507,15 @@ class EditPage implements IEditObject {
 			)
 		);
 		$constraintRunner->addConstraint(
+			new DoubleRedirectConstraint(
+				$this->allowDoubleRedirects,
+				$content,
+				$this->getCurrentContent(),
+				$this->getTitle(),
+				$this->redirectLookup
+			)
+		);
+		$constraintRunner->addConstraint(
 			// Same constraint is used to check size before and after merging the
 			// edits, which use different failure codes
 			$constraintFactory->newPageSizeConstraint(
@@ -2619,6 +2637,8 @@ class EditPage implements IEditObject {
 			$this->selfRedirect = true;
 		} elseif ( $failed instanceof BrokenRedirectConstraint ) {
 			$this->brokenRedirect = true;
+		} elseif ( $failed instanceof DoubleRedirectConstraint ) {
+			$this->doubleRedirect = true;
 		}
 	}
 
@@ -3154,6 +3174,10 @@ class EditPage implements IEditObject {
 			$out->addHTML( Html::hidden( 'wpIgnoreBrokenRedirects', true ) );
 		}
 
+		if ( $this->doubleRedirect ) {
+			$out->addHTML( Html::hidden( 'wpIgnoreDoubleRedirects', true ) );
+		}
+
 		$autosumm = $this->autoSumm !== '' ? $this->autoSumm : md5( $this->summary );
 		$out->addHTML( Html::hidden( 'wpAutoSummary', $autosumm ) );
 
@@ -3374,6 +3398,26 @@ class EditPage implements IEditObject {
 				);
 			}
 
+			if ( $this->doubleRedirect ) {
+				$editContent = $this->toEditContent( $this->textbox1 );
+				$redirectTarget = $editContent->getRedirectTarget();
+
+				$doubleRedirectTarget = $this->redirectLookup->getRedirectTarget( $redirectTarget );
+				$doubleRedirectTargetTitle = Title::castFromLinkTarget( $doubleRedirectTarget );
+
+				$suggestedRedirectContent =
+					$editContent->getContentHandler()->makeRedirectContent( $doubleRedirectTargetTitle );
+				$suggestedRedirectCode =
+					Html::element( 'pre', [], $this->toEditText( $suggestedRedirectContent ) );
+
+				$out->wrapWikiMsg( "<div id='mw-doubleredirect'>\n$1\n</div>", [
+					'edit-constraint-doubleredirect',
+					$buttonLabel,
+					wfEscapeWikiText( $doubleRedirectTargetTitle->getPrefixedText() ),
+					$suggestedRedirectCode,
+				] );
+			}
+
 			if ( $this->hookError !== '' ) {
 				$out->addWikiTextAsInterface( $this->hookError );
 			}
diff --git a/includes/editpage/IEditObject.php b/includes/editpage/IEditObject.php
index 102377fcacf2..873f69f810ad 100644
--- a/includes/editpage/IEditObject.php
+++ b/includes/editpage/IEditObject.php
@@ -120,4 +120,7 @@ interface IEditObject {
 
 	/** Status: user tried to create a redirect to a nonexistent page and wpIgnoreBrokenRedirects is false */
 	public const AS_BROKEN_REDIRECT = 244;
+
+	/** Status: user tried to create a redirect to another redirect and wpIgnoreDoubleRedirects is false */
+	public const AS_DOUBLE_REDIRECT = 245;
 }